Biaxially oriented polypropylene (BOPP) film is an important part of capacitor. The key parameters (ash content, isotacticity, molecular weight, melt flow rate, isotactic sequence length) of polypropylene resin used as raw materials for BOPP films and their influence rules were summarized in this paper. At the same time, the existing production technology of BOPP capacitor film was summarized, and the methods to improve the performance of BOPP film were further reviewed. Finally, it is proposed that the future development of BOPP films for capacitors will focus on the ultra-low ash resin raw materials and heat resistant films.

A series of resins with ≥30% of solid content and about 4 000 mPa·s of viscosity and their polyimide films were prepared by introducing flexible 4,4′-oxobisphthalic anhydride (ODPA) or twisted non-coplanar structure 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride (BPDA) into the molecular structure of homophthalic tetracarboxylic acid dianhydride-4,4′-diaminodiphenyl ether (PMDA-ODA), and capped with a capping agent. The properties of the films were characterized by tensile testing machine, breakdown voltage tester, TMA, DMA, TGA, and cross-cut tester. The results show that when the solid content of the semi-rigid structure PMDA-ODA resin increases to 30% and the viscosity reduces to about 4 000 mPa·s, the film could not be formed due to the low molecular weight, and the PI film with good electromechanical properties can be prepared through introducing flexible monomer to improve the the polymer flexibility and using norbornene diacetic anhydride (NA) for capping. When continuing to increase the resin solid content and increase the proportion of flexible monomers, the electromechanical properties, heat resistance, ahd the adhesion on the copper sheet of the film decrease. The films with 30% of solid content, about 4 000 mPa·s of viscosity, 30% mole fraction of ODPA, and end-capped with NA show better electromechanical properties, heat resistance, and adhesion, which can be used as a impregnating varnish for insulation protection on the surface of substrate.

In this paper, the research progress on new eco-friendly insulating gases at home and abroad was reviewed, and the international mainstream promotion of perfluoroisobutyronitrile (C₄F₇N) gas and its application in electrical equipment were expounded emphatically. The gap and surface insulation characteristics of C₄F₇N gas mixture were summarized, and the design criteria of the related equipment insulation was proposed. The decomposition characteristics and gas-solid compatibility evaluation indices of C₄F₇N gas mixture under different operating conditions were analyzed. Additionally, the research progress on arc-quenching performance of C₄F₇N and its gas mixture and the development and application of a series of eco-friendly equipment were introduced, so as to provide a theoretical reference for the environmental protection upgrade of SF₆ electrical equipment in the current stage. Meanwhile, it was noted that the research and development efforts on new eco-friendly insulating gases with superior performance were still ongoing at home and abroad, which can provide technical support for the construction of a green and low-carbon power grid.

Polyimide (PI) is a class of high-performance polymer materials containing π-conjugated imide ring in the main chain, and its size of the band gap is one of the main factors directly affecting the thermal stability, optoelectronic properties, dielectric properties and other properties of the material. The electrically powered diamine group and the electrically absorbing dianhydride group in the conventional PI molecular structure determine that the value of band gap is nearby 3.0 eV, which directly affects its performance in the field of high-temperature energy storage, high-frequency communication, electrical insulation, etc. Because of the excellent structural designability of PIs, the band gap of PIs can be adjusted by modulating the monomer combination/chain segment structure/space structure, and the above properties of PIs can be optimized. In this paper, based on the main research progresses of PI bandgap modulation reported in recent years, the main strategies of PI bandgap modulation were elaborated from the perspectives of polymer structure and adjusting polymerization process, respectively, and the difficult problems faced in PI bandgap modulation were discussed with the example of its application in the field of dielectric energy storage. Finally, the future development direction of PI bandgap modulation was discussed on the basis of current research status of PI bandgap modulation.

In this paper, the characteristics of high-frequency copper clad laminates were summarized, the dielectric properties of their base resins were compared, and the research progresses of hydrocarbon resin (PCH) high-frequency copper clad laminates were mainly introduced. By summarizing the current researches on hydrocarbon resin based high-frequency copper clad laminates, the existing problems were pointed out, and their future development trends were prospected.

In this paper, the basic research and application progress of high temperature resistant epoxy molding compound (EMC) at home and abroad in recent years were reviewed. The property requirements of advanced power electronics on the molding compound, the high temperature degradation mechanism of traditional EMC, the relationship between structure and thermal stability of EMC, and the modification pathways for improving the thermal stability of EMC were presented. Especially, the development status of multi-aromatic ring (MAR) and naphthalene-containing EMC were reviewed. At last, the future development trends of high temperature resistant EMC for power electronic packaging were prospected.

Epoxy resin and its composite materials play a major insulation role in electrical apparatus due to their excellent thermodynamic and electrical insulating properties. With the gradual development of electrical apparatus towards high voltage and high power, as well as the continuous rise of voltage levels, the performance requirements for epoxy insulating materials inside electrical apparatus are increasingly increasing. This paper focused on epoxy resin insulating materials for high-voltage electrical apparatus, and reviewed the current research and application progress from three aspects: formulation composition, curing process, and performance improvement of insulation systems. It was aimed to establish the relationship between the composition, structure, and macroscopic properties of epoxy insulation systems, provide suggestions and prospects for the development direction of domestic epoxy resin insulating materials in the future, and accelerate the localization development of epoxy resin materials for high-voltage insulation.

In high-voltage insulated gate bipolar transistor (IGBT) devices, traditional Si-based semiconductor chips are gradually replaced by emerging wide-bandgap semiconductor chips. High-power-density wide-bandgap semiconductors lead to a sharp rise of operating temperature in power electronic modules. Silicone gel is used as an insulating material for the packaging of high-voltage IGBT devices, and its insulating performance faces the challenges of high temperature and thermal ageing. In order to study the effects of high temperature and thermal ageing on the thermal stability and insulating properties of silicone gel, we studied the effects of high temperature and long-term thermal stress on the dielectric properties, volume conductivity, and breakdown strength of silicone gel by high temperature experiments and thermal ageing experiments of silicone gel materials, and analyzed the high temperature characteristics and thermal ageing characteristics of the silicone gel. The results show that with the increase of temperature, the real part of complex permittivity and breakdown strength of silicone gel decreases, and the dielectric loss and DC conductivity increases. With the increase of thermal ageing time, the real part of complex permittivity of silicone gel increases, the dielectric loss decreases at first and then increases, the DC conductivity increases at first and then decreases, and the breakdown strength decreases.

To address the challenges of epoxy resins in electrical insulation and flame-retardant applications, a phosphorus-containing bio-based flame-retardant resin—bis(methacryloyloxy-4-hydroxy-3-methoxyphenyl) phenyl phosphate (DGEBDB) was synthesized from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and renewable vanillin, and cured materials were prepared through blending it (0%, 25%, 50%, and 75%) with bisphenol A epoxy resin (DGEBA). Their flame retardancy, thermal properties, mechnical properties, and electrical properties were analyzed. The results show that when the mass fraction of DGEBDB is 75%, the limiting oxygen index (LOI) of epoxy bending system increases from 22.6% to 34.2%, and the flame retardant grade achieves V-0 in UL 94 tests. Cone calorimetry reveals that the DGEBDB can reduce the heat release rate (HRR) and total heat release (THR), showing excellent fire suppression. Electrical properties tests show that the electrical properties of the cured epoxy maintain good when the mass fraction of DGEBDB is as high as 75%, which ensures the reliability of DGEBDB in electrical application. Mechanical properties indicate that with the increase of DGEBDB content, the flexural strength and tensile strength increase, indicating an increase in structural integrity and load bearing capacity of the cured epoxy. Therefore, the addition of DGEBDB significantly enhances the flame retardantcy of composite, while maintaining the excellent thermal, mechanical, and electrical properties of epoxy resin, and when the mass fraction of DGEBDB is 25%, the overall performance is the best, which has a better prospect for practical applications.

In this paper, the research progresses of functional polysiloxane, silane coupling agent, POSS, and other organosilicon modified epoxy resins were reviewed from two aspects of physical and chemical modification. Combined with the development demand of material science, it was proposed that the water-based and photocurable environment-friendly silicone modified epoxy resin would be the future development direction.